The present invention relates generally to an automatic tire changing machine and more particularly to the positioning pin thereof.
Automatic tire changing machines are presently available in numerous configurations. Generally the wheel assembly, i.e., the rim and tire, is mounted on a platform in a substantially horizontal orientation. The wheel assembly is secured about a rotatable shaft which extends through the central aperture of the rim.
Thereafter the machine is actuated and two shoes engage and loosen the tire beads. A mount/dismount tool is mounted on the rotatable shaft and inserted between the rim and tire bead. Rotation thereof lifts the tire bead over the rim, providing the desired separation.
To eliminate the possibility of wheel or rim rotation as the shaft and mount/dismount tool rotate, the majority of automatic tire changing machines include a positioning pin. This pin is generally installed at a single, maximum preset height above the wheel-supporting platform of the tire changing machine. The pin extends through the wheel-supporting platform and engages one of the lug holes in the rim.
The lug holes are located in the rim web. The distance between the rim web and the platform of the tire changer (referred to as rim offset) varies substantially from wheel assembly to wheel assembly. For example, the distance for a Volkswagen "Bug" wheel assembly is substantially less than that for a Buick "Electra" wheel assembly. On rims with an offset greater than the standard installed height of the positioning pin, a seperate positioning pin extension is generally placed over the positioning pin to increase its effective height.